Rhus verniciflua (or Rhus vernicifera) is a deciduous tree belonging to the Anacardiaceae family. This plant is indigenous to the Central Asian highlands and Himalayan regions, and is currently distributed throughout the world, particularly in the subtropical regions including the tropical regions and also in the temperate regions. The plant is cultivated in the Northeast Asian region including Korea, Japan and China, mainly for the purpose of obtaining lacquer.
The sap of Rhus verniciflua is referred to as lacquer, and dried lacquer has been traditionally known in the Oriental medicine to have the functions of removing extravasated blood, promoting blood circulation and having efficacy against intestinal worms, abdominal pain, hyperacidity, coughs, tuberculosis, amenorrhea, constipation, diabetes mellitus, malaria and the like. Recently, dried lacquer has been reported to have an anticancer effect (Namba, T., Colored Illustrations of Wakan Yaku. p 215, Hoikusha Publishing Co. Ltd., Osaka, 1980).
In Korea, Rhus verniciflua has been used in special dishes for restorative or medicinal purposes, such as lacquer chickens, lacquer ducks and the like. Furthermore, the sap of the Rhus plant has useful properties such as durability which makes the plant to be used as a natural coating material, and chemical resistance which makes the plant to be used as a special exterior coating material for aircraft, ships, submarine optic cables and the like.
However, a person who is highly sensitive to lacquer may suffer from dermatitis (allergies) even upon brief contact with lacquer, and thus most people tend to avoid contacting with lacquer. In fact, the ratio of the population showing no sensitive responses against lacquer is only about 20 to 40%.
The component in lacquer which induces allergy as such is urushiol, which is one of the main components of the sap of Rhus verniciflua. The component is a dark brown liquid used in lacquerwork, and it is highly soluble in organic solvents. The principal chemical structures of urushiol include side chains having 15 to 17 carbon atoms, with a number of unsaturated bonds being present in the chains. Urushiol itself is a strong allergy causing material and that is the major restriction in obtaining pharmacological effect from the intake of the extract.
The main components that are reported to exhibit the pharmacological efficacy of Rhus verniciflua are urushiol, fustin, fisetin, sulforetin, butein and the like, and studies have been made on the compositions based on these components and functions thereof.
The main pharmacological actions of lacquer that are known include the anticancerous and antioxidative actions, the hangover-curing action and the like (Korean J. Food Sci. Technol., 31, 238-245 (1997)). In addition, lacquer is known to have efficacy against gastric diseases, heart diseases, arthritis, hypertension, diabetes, stroke, arthritis, chronic fatigue and the like.
Despite such various pharmacological actions, lacquer has not been commercialized yet because of its toxicity to human body. Therefore, there is a strong demand for a method which can provide the maximal pharmacological efficacy of Rhus verniciflua, and which can minimize allergies upon intake of the Rhus plant or an extract thereof, from the perspective of commercializing the plant or the extract.
Heretofore, as the process for preparing an extract of Rhus verniciflua while removing its toxicity, disclosed are a process for preparing Rhus verniciflua health beverages by adding alder tree components (see Korean Patent Application Publication No. 2001-0035052); and a process for preparing beverages by boiling Rhus verniciflua in water together with pine leaves, mulberry roots, Amomi semen and the like (Korean Patent Application Publication No. 1995-0023317). These processes involve merely boiling the Rhus plant together with other added materials to reduce the toxicity of the Rhus plant. Thus, the processes could not sufficiently eliminate toxicity and thus, hardly succeeded in commercializing the Rhus extract.
Furthermore, a process involving fractionation (Korean Patent Application Publication No. 2002-0002096), a process involving leaving an ethanol extract of the plant to stand for a length of time (Korean Patent Application Publication No. 2003-0079255) and the like, use column chromatography as a final process to extract active ingredients and to eliminate toxicity. Thus, there are problems such as complicated process, lengthened processing time and high costs.
In addition to these, heat treatment techniques have been suggested, such as a process for eliminating toxicity through the steps of hot air drying and solvent extraction (Korean Patent Application Publication No. 2002-0023439) and a process for removing toxic substances by heat treatment (Korean Patent No. 0394089). However, these processes involve heat treatment at a high temperature ranging from 100 to 400° C., and thus, may cause side effects such as destruction of the active ingredients that are thermally labile.
Meanwhile, techniques for extracting specific active ingredients of Rhus verniciflua and uses thereof have been suggested as described below. Most of these techniques have been developed with focusing on the extraction of components such as urushiol, fustin, fisetin and the like.
Examples of such techniques include: New use of urushiol derivatives as an anti-cancer medicine including anti-oxidative activity and method of preparation thereof (Korean Patent Application Publication No. 1997-0013163 and Korean Patent No. 0215390); a manufacturing method of extract of Rhus verniciflua STOKES having high antioxidant activity (Korean Patent Application Publication No. 2003-0079255); use of an extract of Rhus verniciflua having inhibitory effects of reverse transcriptase (Korean Patent Application Publication No. 2002-0084333); a hepatoprotective composition comprising an extract of Rhus verniciflua having fustin, fisetin, sulfuretin, butein and the like as main components (Korean Patent Application Publication No. 2002-0077833); a liver disease treating agent containing the extract and flavonoid compounds isolated from Rhus verniciflua STOKES (Korean Patent Application Publication No. 2004-0043255); and the like, and extraction and separation of the above-described components were usually carried out using silica columns.